This invention relates to bearing supports for large, rotating shaft, turbomachines; and, in particular, is related to a self-aligning journal-thrust bearing and bearing support.
Many kinds of machines have rotating shafts or rotors which can develop large axial thrust forces. Typically, a collar or runner on the shaft transmits the thrust load to a stationary thrust bearing. One common type of thrust bearing is a tapered land thrust bearing. The bearing face is divided into several lands separated by radial oil supply grooves. These grooves have dams at their outer ends and are supplied with oil under pressure to give controlled and positive oil feed to the inlet edges of the lands. Each land is made with a fixed sloping bearing surface creating the hydrodynamic oil film wedge necessary to produce high thrust load carrying capability during operation. It is known that tapered land thrust bearings can withstand very high loads when properly aligned. A small flat area at the trailing edge of each land is made parallel to the thrust runner to carry thrust loads when starting or at low turning speeds.
In a steam turbine, many thrust bearing failures are related to misalignment, often aggravated by high thrust loads due to water induction. Misalignment can occur when high thrust loads cause deformation and tilting of the stationary bearing pedestal or if the bearings supporting the rotor move radially relative to each other due to differential thermal expansion in the pedestals and foundations. It is therefore desirable to incorporate a self-aligning capability into a bearing structure to allow the stationary thrust bearing to conform to the orientation of the rotating thrust runner under operating conditions. Equal or nearly equal loading on the various lands of the thrust bearing is thereby maintained at all times.
It is one object of the present invention to provide a bearing support structure capable of accommodating angular rotor misalignments.
It is another object of the invention to provide a bearing support structure which is very stiff in the axial and radial directions and reasonably flexible in a tilting mode to accommodate angular misalignment in the rotor.
The novel features believed characteristic of the present invention are set forth in the appended claims. The invention itself, however, together with further objects and advantages thereof, may best be understood with reference to the following description taken in connection with the included drawings.